The present invention relates to electromagnetically controlled valves, referred to hereinafter as "electrovalves" intended to allow a relationship between the partial vacuum originating in a vehicle engine and various pieces of equipment and devices whose operation may be controlled by such partial vacuum, the considerable power of which is known to be generally lost once the valves have been operated. Among such devices there are, for instance, air-conditioning distribution shutters, driving members for the anti-pollution device, a speed regulator, retractable lights, a central locking system for doors, the roof and the trunk and similar items.
Electrovalves of this type are already known in the art and have, at one end, a connecting pipe to the apparatus to be controlled opening into the body of the valve without an outlet stopping member and, at the other end, a pair of pipes, the first being connected to the partial vacuum origin and the second opening either on the outside or at the supply of a second similar electrovalve connected in series to the first one, one of the two latter pipes being open when the other is closed and vice-versa. There follows that the apparatus to be controlled is constantly connected either to the partial vacuum in the engine or to the outside, or to another similar system operated by the residual partial vacuum in the engine to which we shall generically refer as an outlet region.
As a rule, these two pipes are arranged coaxially on the two opposite end faces of the valve body and the alternate blocking and opening of the two pipes is generally controlled by the axial translation of the core of an electromagnet, whose armature and winding are also located inside the mentioned body, each end of the core being fitted with a pad made of a material acting as a seal. The pad disposed adjacent the connection to the partial vacuum origin is usually restored, by means of a return spring, against the seat provided by the mouth of the pipe; whereas, the other pipe stays open as long as the electromagnet is not excited.
When the user wishes to work one of the devices listed above by way of examples, he operates a switch which excites the electromagnet, thus causing an axial movement of the core against the spring and connecting the partial vacuum origin to the mentioned device and simultaneously closing "the outlet" by the interposition of the other pad acting as a seal which comes to rest on the outlet seat.
This type of device is very simple and widely used, but it still has a number of drawbacks.
Firstly, heretofore, these known devices have been equipped with return springs positioned around the core inside the coil, hence the coil is less powerful and more cumbersome.
Secondly, since the material of which the two pad seals are made has to withstand significant stresses, from the chemical (corrosion), physical (wide temperature variations), and mechanical (slanting surfaces resting against circular openings made on flat surfaces) points of view, it has to be selected from among very costly elastomers; additionally, it is in any case necessary to provide two seals for each valve and this doubles the amount of sealing material required for each valve.